A Sikh truck driver in the US has alleged that traffic police in Mississippi called him a "terrorist" and a county judge later humiliated him by describing his turban as "that rag."

Jagjeet Singh, 49, a trucker from California, was driving through the Mississippi State when he was pulled over for driving with a flat tyre in Pike County on January 16, according to a complaint filed by the American Civil Liberties Union (ACLU) and United Sikhs.

Police officers called Singh a "terrorist" and had him arrested for declining to remove his kirpan, a small, sacred sword of the Sikh faith, which Singh was lawfully wearing in accordance with his religious beliefs.

When he returned to Mississippi for his court date in Pike County, Judge Aubrey Rimes ordered him out of the courtroom because he did not like his turban - calling it "that rag" - and threatened to punish him unless he removed it, the ACLU said in a press release.

"The officers' shameful treatment of Mr. Singh was an abuse of their authority and a betrayal of the public's trust that law enforcement officials will carry out their duties free from prejudice," said Bear Atwood, legal director at the ACLU of Mississippi.

"The fact that officers may be unfamiliar with Sikhism or other minority religions does not give them license to harass and degrade members of the public who follow those faiths," Atwood said.

The letter sent to the Mississippi Department of Transportation (MDOT) officials demands that they provide public documents relating to Singh's detainment and arrest and urges them to implement an ongoing training programme to educate officers about their responsibility to treat every person with dignity and to remain respectful of religious diversity.

Sikhs deserve the same protections as all other people of faith. No person should be harassed and discriminated against by law-enforcement and judicial officers merely because he practices a minority religion, Manmeet Singh, staff attorney for United Sikhs, said.

In response to an investigation by the US Department of Justice, the county revised its harassment and non- discrimination policy to explain that religious discrimination includes forcing an individual to remove religious head coverings.

The ACLU and United Sikhs said they plan to file a separate complaint with the Mississippi Judicial Commission, asking officials to investigate Judge Rimes's conduct and impose appropriate sanctions.